Fig. 2. Conceptual diagram for how the downsizing of the biosphere (the sequential loss of the megabiota) influences the total amount of ecosystem stock (biomass, carbon, nutrients), productivity, or fertility.

In (a), for assemblages of either plants or animals,  there is an inverse relationship between size and abundance. But, as larger organisms are disproportionately more prone to population reduction and extinction than smaller organisms, this leads to a reduction in the number of larger body sized individuals and a reduction in their numbers. As a result, past extinction and continued hunting, fishing, land and water use pressures in addition to climate change, are compressing body size distributions across most of the worldʼs ecosystems. In (b) metabolic scaling theory and empirical data show that communities and ecosystems with larger body sized plants and animals flux more energy and resources. As a result, continued reductions in body size in (a) will lead to a continued reduction in ecosystem stocks and flux of energy and nutrients.